Thinking about stopping into a living, breathing house of worship on your next trip? Matlins and Clooney suggest keeping these things in mind, regardless of the place's faith tradition:

Be respectful. "You are in a place that is special and holy to other people," Matlins says. "Dress and behave appropriately so you do not disturb their sense of the specialness and holiness of the place."

Pay attention. You want to "be sensitive to what is expected of the visitor -- either to hold back, or to participate more fully," says Clooney. "Being too forward or too passive may both be offensive." Also, "be careful to note where and how far into the space one is welcome. Some areas are more sacred than others."

Follow along. Observe "the customs of the community -- removing shoes, covering heads, the segregation of men and women, talking or not, taking photos or not, in accord with custom," says Clooney.

Listen with your "third ear." "You may not understand the language," says Matlins, "but you can hear the feelings if you open yourself up to them."

Sit in the back. Not only does it keep you from appearing intrusive, but it can minimize any innocent missteps. Suggests Matlins: "Do what you see other people do, unless it violates the tenets of your own faith."

Who knows, perhaps through these spiritual experiences you'll discover what so many travelers find: Despite people's very real differences across nationalities, cultures and faiths, it's what they share in common that matters.